Holesaw

ABSTRACT

A holesaw includes an arbor for supporting a pilot drill and a bell-shaped sawblade. The sawblade is attached to a lower threaded portion of the arbor. A pin support with at least one pin engages the top of the holesaw blade and is axially movable but not rotationally movable relative to the arbor. A clamping sleeve is threaded onto an upper threaded portion of the arbor. The clamping sleeve can be screwed down to press against the bell top of the sawblade. A spring may be disposed between the clamping sleeve and the pin support.

BACKGROUND

Holesaws are used with power drills to make large diameter holes inrelatively thin materials with limited machine power, since they convertonly a limited annular region to sawdust and chips. Traditionally,holesaws comprise an arbor with one or more threaded areas, a centralpilot drill attached to the arbor, an axially movable pin support whichis rotationally locked to the arbor and provided with one or more pins,and a bell-shaped holesaw blade which is made to rotate with the arborby the pins penetrating pin holes in a flat top of the bell. Therotational locking of the pin support to the arbor occurs usually byhaving a profiled hole in the pin support slide along a correspondinglyprofiled part of the arbor as in patents U.S. Pat. Nos. 4,063,560 and5,076,741, or by having a flange fixed to the arbor acting directly onthe pins as in patents U.S. Pat. Nos. 4,669,928 and 4,968,189. The uppershank of the arbor is made for easy attachment to the power drill,conical, cylindrical or hexagonal.

One common demand when using holesaws is that it should be possible toexchange the sawblade without removing the other components from thepower drill. For this purpose the sawblade has a threaded center holeattached to a threaded end of the arbor, and can be quickly removed byrotating it after moving the pin support axially to disengage the pinsfrom the top of the bell. To allow drilling vertically upwards, the pinsupport must be securable against unintentional displacement, as by alocking spring in U.S. Pat. No. 4,036,560 or by a nut as in U.S. Pat.No. 4,669,928.

The holesaw is rotationally guided by the pins and axially by thethreaded center hole. Modem sawblades are often made from thin walledmaterial, which makes the thread prone to wear, and the top of the bellhas a low stiffness for axial and tilting motions. Therefore, it ispreferred to press an end surface of the pin support against the top ofthe bell by a snap lock spring as in U.S. Pat. No. 4,036,560, by aspring loaded washer as in U.S. Pat. No. 3,784,316 or by a nut as inU.S. Pat. No. 3,758,221. It has also been suggested in application SE 9503797-4 to press against the top of the bell the end of a tubular sleevelocated concentrically outside the pin support by rotation of the samenut that secures the pin support axially, in order to apply the force ata greater radius measured from the arbor.

All mown designs of holesaws have disadvantages in common. If they use anut or a spring loaded washer, two hands are needed for changingsawblade. If they use a snap lock spring, neither the size nor thesymmetry of the load is controlled. The present invention concerns a newtype of holesaw where a change of sawblade can be made with one hand.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understoodby reading the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

FIG. 1 is a partially cross-sectional view of a holesaw according to anembodiment of the present invention, with components positioned formounting or dismounting; and

FIG. 2 is a partially cross-sectional view of a holesaw according to anembodiment of the present invention when ready for use.

A holesaw of the type according to the invention is shown in FIG. 1 and2 and comprises an arbor (11) with one or more threaded portions (12,13)and a pilot drill at the lower end, a bell-shaped sawblade consisting ofa flat bell top (14) with a center hole (15) which can be attached tothe lower threaded portion (13) of the arbor and an annular sawing part(16), a pin support (17) which is rotationally locked to the the arbor(11) and provided with at least one pin (18) which can penetrate acorresponding pin hole (19) in the bell top (14) to transfer torque tothe sawblade.

A holesaw according to the invention also comprises a clamping sleeve(20) concentrically surrounding the pin support (17) and threaded ontoan upper threaded portion (12) of the arbor, and a spring (21) actingbetween the clamping sleeve and the pin support The clamping sleeve hasmeans for restricting the downward displacement of the pin support (17)and lifting it when the sleeve is moved upward, such as inward pointingpegs or a spring washer (22), and its outer surface has such an exteriorsurface structure that it can be easily turned by hand.

FIG. 1 shows that when the arbor is ready for mounting of a sawblade,the clamping sleeve (20) should be high up on threaded portion (12). Thepin support (17) when the clamping sleeve is pressed by the spring (21)down against the lifting means (22), the pins (18) protruding below theedge of the clamping sleeve. The pin support is axially movable alongthe arbor, but rotationally restricted by wedge grooves, splines or flatmilling of a portion (24) of the arbor bet the upper (12) and the lower(§13) threaded portions. The sawblade can now be threaded onto the lowerthreaded portion (13) of the arbor, since the center hole (15) in itsbell top (14) is threaded if the material thickness is sufficient, or isprovided with a threaded collar. The sawblade is rotated until it isimmediately below the clamping sleeve and the bell top is touched by thepins (18). During continued rotation the pin holder (17) is lifted untilthe pin holes (19) are right below the pins (18) which are then presseddown into the pin holes by the spring (21) to stop further rotation.Thereafter, the clamping sleeve (20) is screwed downward until its loweredge (23) axially supports the bell top (14) of the sawblade in anannular region surrounding the pins (18) and the pin holes (19) as shownin FIG. 2. The holesaw is then ready for use, and is much more stablethan conventional holesaws where axial forces are only applied at thecenter thread (15).

When a sawblade is to be changed, the clamping sleeve (20) is screwedupward so that its lower edge (23) first loses contact with the bell top(14), and subsequently the lifting means (22) lifts the pin holder (17)to disengage the pins (18) from the pin holes (19), as shown in FIG. 1.After that, the sawblade is rotated in the opposite direction until itcan be taken off the lower threaded portion (13) of the arbor.Preferably, the clamping sleeve is then screwed a short distancedownward to make ready for mounting a new sawblade.

On a holesaw according to the invention, the underside of the pin holder(17) and the lower edge (23) of the clamping sleeve should beapproximately at the same level to cause the lowest possible bendingstress in the pins (18). The holesaw is independent of metal particlesor small deformations or tapering near the center hole, which would onlycause the pin holder to settle at a slightly higher level. Should anyparticles be stuck between the sleeve edge (23) and the bell top (14),his is easy to notice and remove.

If the upper and lower portions (12,13) of the arbor are long enough,preferably continuous with the same read diameter, and the sawn-out plughas stuck inside the sawblade, as commonly happens when sawing wood orplastics, it is possible to remove the plug by first screwing theclamping sleeve far upward to a position corresponding to FIG. 1,thereafter also the holesaw blade upward until the plug is forciblyremoved by the lower end of the arbor.

It is also possible to make the threaded portions (12,13) with differentdiameters, not continuing over the intermediate portion (24), which maysimplify assembly of the clamping sleeve (20).

While this invention has been illustrated and described in accordancewith a preferred embodiment, it is recognized that variations andchanges may be made therein without departing from the invention as setforth in the claims.

What is claimed is:
 1. A holesaw comprising:an arbor adapted to supporta pilot drill; a sawblade with a bell top and an annular sawing partattached to the top; a pin support including at least one pin; aclamping sleeve; the pin support being non-rotatable relative to thearbor but axially displaceable along a portion of the arbor; theclamping sleeve being rotatably threaded on an upper threaded portion ofthe arbor and concentrically enclosing the pin support with only the atleast one pin projecting below an edge of the clamping sleeve to engageat least one corresponding pin hole in the bell top, the bell top beingattached to a lower threaded portion of the arbor; the pin support beingaxially movable between an upper and a lower position within theclamping sleeve; and a spring for pressing the pin support towards thelower limiting position.
 2. A holesaw according to claim 1, wherein theupper threaded portion is long enough to permit the clamping sleeve tobe screwed down until the lower sleeve edge presses against the bell topof the sawblade threaded onto the lower threaded portion of the arbor.3. A holesaw according to claim 1, wherein the portion of the arboralong which the pin support is displaceable is non-circular and includesone or more key grooves.
 4. A holesaw according to claim 1, wherein theportion of the arbor along which the pin support is displaceable isnon-circular and includes one or more flat faces.
 5. A holesaw accordingto claim 1, wherein the upper and lower portions of the arbor have acontinuous thread and are of equal diameter.
 6. An arbor for a holesaw,comprising:an arbor having an upper threaded portion, a lower threadedportion, and a middle portion between the upper and lower threadedportions, the arbor being adapted to support a pilot drill at a lowerend thereof and a sawblade with a bell top and an annular sawing part onthe the lower threaded portion; a pin support including a pin extendingfrom a bottom surface of the pin support, the pin support being mountedon the middle portion of the arbor and being axially displaceable butnon-rotatable relative to the arbor; a clamping sleeve screwed onto theupper threaded portion; and a spring disposed around the arbor betweenthe clamping sleeve and the pin support.
 7. The arbor as set forth inclaim 6, wherein the clamping sleeve includes an annular portionsurrounding the spring.
 8. The arbor as set forth in claim 7, whereinthe clamping sleeve includes an annular portion surrounding the pinsupport.
 9. The arbor as set forth in claim 6, wherein the clampingsleeve includes an annular portion surrounding the pin support.
 10. Thearbor as set forth in claim 6, wherein the arbor includes an axialopening for receiving the pilot drill.
 11. The arbor as set forth inclaim 10, wherein the arbor includes a set screw for locking the pilotdrill relative to the arbor.
 12. The arbor as set forth in claim 6,wherein the middle portion of the arbor is non-circular.
 13. The arboras set forth in claim 12, wherein the middle portion of the arborincludes at least one key groove for receiving at least onecorresponding key on the pin support.
 14. The arbor as set forth inclaim 12, wherein the middle portion of the arbor includes at least oneflat face.